DRS Anti-afinity rules for multi-instance component

I have a blueprint for a cluster.  It has a single vSphere VM on it that allows 3..4 instances (numbers kept small for this explanation).  I want to put half of the VMs in one VM group and the other half in another VM group. (The groups are pre-defined with a vSphere DRS anti-affinity rule).  This way, if I loose a server, worst case scenario is I loose half of the cluster.

My problem:  How do I tell  in post-provisioning if this is instance 0, 1, 2 or 3 so that I can put the VM into the correct VM group.  Instance 0 and 2 should go to VM group A and instance 1 and 3 should go to VM group B.  In vRO, I can not find any properties that allow me to identify the instance.  This gets further complicated with scale-in/out.

Thanks,

Carl L.